German Published Patent Application No. 199 49 286 describes a device for regulating at least one vehicle motion variable describing a motion of a vehicle. To this end, the device contains regulator means with which actuators are triggered for regulating the vehicle motion variable. Furthermore, the device contains determination means with which a bad stretch of road variable, which describes the vehicle""s drive on a stretch of bad road, is determined. The regulator means is influenced as a function of the bad stretch of road variable, such that the sensitivity of the regulator means is adapted to the vehicle""s drive on a stretch of bad road. European Patent No. 0 339 056 describes a method of regulating the stability of a vehicle in traveling along a curve, where the vehicle speed and the coefficient of friction between the tires and the road are determined. In this method, the steering angle and the rate of rotation of the vehicle about the vertical axis (yaw rate) are also determined, and a lower limit value characteristic of the yaw rate is determined as a function of the steering angle, taking into account the vehicle speed and the coefficient of friction. The brake pressure is reduced when the measured yaw rate drops below the limit value characteristic. German Published Patent Application No. 199 64 032 describes a method and a device for stabilizing a vehicle. In this method, a transverse dynamics variable which describes the transverse dynamics of the vehicle is regulated to stabilize the vehicle. The transverse dynamics variable is regulated by limiting the float angle of the vehicle to a predetermined value. Regulation of the transverse dynamics variable is altered by input by the driver to allow a larger float angle than the predetermined value.
In vehicle dynamics control (VDC) systems (ESP=electronic stability program), the driver selects a desired driving performance by selecting the steering angle. A setpoint for the yaw rate is calculated as a function of the steering angle, the transverse acceleration and the longitudinal speed of the vehicle. If the measured yaw rate does not match the calculated setpoint yaw rate, the vehicle dynamics controller will attempt to adapt the yaw rate to the setpoint, e.g., through changes in brake pressure on the individual wheels or through active steering operations. The phase shift between the change in the steering angle and the change in the yaw rate due to the inherent dynamics of the vehicle is taken into account through suitable filters. It is desirable, especially with certain sporty vehicles, to tolerate an admissible system deviation between the setpoint yaw rate and the actual yaw rate in many cases. Suitable measures are performed to suppress the vehicle controller intervention measures in these cases.
With the known implementations, it is impossible to allow greater permanent system deviations between the yaw rate setpoint and the actual yaw rate depending on the situation. Thus, in the case of front-wheel-drive vehicles, for example, it is impossible to steer back in coming out of a turn on a smooth road surface and to straighten out the vehicle again slowly merely by accelerating without any active braking intervention by the vehicle dynamics controller. However, that is precisely what is often desired in the case of sporty vehicles. Stabilizing measures should be taken only when the driver must definitely countersteer (xe2x80x9ccountersteeringxe2x80x9d means that the steering angle is rotated in the opposite direction, past the zero position) or when the float angle of the vehicle increases. If the driver steers back only slightly (xe2x80x9csteering backxe2x80x9d means that the steering angle is reduced but is not rotated in the other direction, past the zero position), then the regulator should assume the stabilization function and should intervene with full sensitivity. If the driver steers back forcefully, this is sufficient with a suitably tuned vehicle to straighten the vehicle out even without a braking intervention measure. It is thus important to prevent the stabilization measure on the part of the driver (due to steering back forcefully) to be superimposed on that of the regulator (through a braking intervention measure on the front wheel which is on the outside of the turn, for example), in which case the stabilization may subjectively appear to be too intense. The present invention described here opens up the possibility of expanding the known vehicle dynamics control (VDC, ESP) in the manner described above.
The present invention relates to a device for regulating at least one controlled variable of vehicle dynamics which describes a motion of a vehicle, the device
containing the determination means with which at least one vehicle dynamics variable is determined, and
containing regulator means for triggering actuators for regulating the at least one vehicle dynamics controlled variable, the sensitivity of the regulator means being influenceable.
The advantage of the present invention is that the sensitivity of the regulator means in at least one operating state of the vehicle is influenced by at least one of the vehicle dynamics variables thus determined.
The vehicle dynamics variables determined by the determination means may, of course, also include the vehicle dynamics controlled variables.
An advantageous embodiment of the present invention is characterized in that at least one transverse acceleration variable and one steering angle variable are determined as vehicle dynamics variables by the determination means, and the sensitivity of the regulator means is influenced
when the operating state is driving with a transverse acceleration of the vehicle different from zero and driver-operated steering against the direction of transverse acceleration or
when the vehicle is oversteered as the operating state and is traveling with a transverse acceleration of the vehicle different from zero, and driver-operated steering is occurring in the direction of transverse acceleration.
Another advantageous embodiment of the present invention is characterized in that at least one transverse acceleration variable and one steering angle variable are determined by the determination means as vehicle dynamics variables, and the sensitivity of the regulator means is influenced
when the operating state of the vehicle is traveling with a transverse acceleration which is different from zero and driver-operated steering is occurring against the direction of transverse acceleration, or
when the operating state of the vehicle is an oversteered state and the vehicle is traveling with a transverse acceleration which is different from zero and driver-operated steering is occurring in the direction of transverse acceleration, the oversteered state being defined in particular by the actual yaw rate exceeding the setpoint yaw rate in absolute value.
It is also possible to define the term xe2x80x9coversteeringxe2x80x9d as follows: oversteering is when the tire slip angle on the rear axle increases more rapidly than the tire slip angle on the front axle with an increase in transverse acceleration.
In an advantageous embodiment, the present invention is characterized in that two different vehicle dynamics variables thus determined are compared, and the sensitivity of the regulator means is influenced differently, depending on the outcome of this comparison.
Another advantageous embodiment is characterized in that
at least the steering angle and the transverse acceleration are determined by the determination means as vehicle dynamics variables, and
the plus or minus signs of the steering angle and the transverse acceleration are compared in this comparison.
It is advantageous if the vehicle dynamics variables thus determined include at least one measured yaw rate and one yaw rate determined by a mathematical model in particular.
An advantageous embodiment is characterized in that
the vehicle dynamics variables thus determined also include the transverse acceleration and the longitudinal speed of the vehicle, and
the absolute value of the yaw rate determined by the mathematical model is limited at the upper end by an upper limit value, at least the transverse acceleration and the vehicle longitudinal speed being used in determining the upper limit value.
It is advantageous
if a driver-independent triggering of the actuators takes place to regulate the at least one vehicle dynamics variable to be regulated if the deviation in the measured yaw rate from the yaw rate determined by a mathematical model, multiplied by a factor, exceeds a maximum allowed limit value, and
if the sensitivity of the regulator means is determined by this factor.
Multiplying the deviation between the measured yaw rate and the yaw rate determined by a mathematical model is equivalent to scaling. This permits an especially robust, inexpensive, and uncomplicated means of attenuating the stabilization measures.
In an advantageous embodiment, the factor has a value between zero and one,
the value zero indicating deactivation of the regulator means, and
the value one indicating operation of the regulator means at maximum sensitivity.
It should be pointed out that the advantageous embodiments mentioned above do not require any additional sensors besides the sensors that are present anyway in a vehicle dynamics control system. This means that no major increase in hardware complexity is required. It should also be pointed out that the vehicle dynamics control system is not completely altered by the present invention. Instead, in many embodiments, the present invention is limited to a variation of intervention threshold values of the vehicle dynamics control system as a function of vehicle dynamics variables.